Middleware

Middleware

go-zero supports middleware at two levels: server-wide and per-route via the API spec.

Server-Wide Middleware

main.go

func LogMiddleware(next http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        log.Printf("-> %s %s", r.Method, r.URL.Path)
        next(w, r)
    }
}

server := rest.MustNewServer(c.RestConf)
server.Use(LogMiddleware)

Per-Route Middleware via API Spec

@server (
    middleware: CheckHeader
)
service user-api {
    @handler CreateUser
    post /users (CreateUserReq) returns (CreateUserResp)
}

goctl generates a stub in internal/middleware/:

internal/middleware/checkheadermiddleware.go

func (m *CheckHeaderMiddleware) Handle(next http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        if r.Header.Get("X-App-Version") == "" {
            httpx.Error(w, errors.New("missing X-App-Version header"))
            return
        }
        next(w, r)
    }
}

Register in ServiceContext:

func NewServiceContext(c config.Config) *ServiceContext {
    return &ServiceContext{
        Config:      c,
        CheckHeader: middleware.NewCheckHeaderMiddleware().Handle,
    }
}

Built-In Middleware

Middleware	Purpose
RecoverHandler	Recover from panics
PrometheusHandler	Prometheus metrics
TracingHandler	OpenTelemetry tracing
MaxBytesHandler	Limit request body size
TimeoutHandler	Per-request deadline